[tevake]

Hey Motion, sounds like you have a fun trip in mind.

Train travel in SE asia can be really nice. We took the train from Bangkok to Chang Mai and enjoyed the overnight trip.
A good friend has been spending winters in Thailand for years, and has had to travel out of country each time to renew his visa. Vietnam is one of the neighboring countries he has visited. He ended up scoring a nice deal on a mid sized touring bike in Bangkok and rode it on many of the visa trips. when he resold the bike in Chang Mai after a few years of owning it he lost very little money. perhaps that could be a way for you to do the trip you want.
I would be happy to put you in touch with my friend if you want.

Cheers Richard